A Longoni-Chini cluster, [Ptl5(C0),l2-, was prepared on MgO powder by a surfacemediated synthesis from Na2PtCb the presence of CO. The formation of [Pt15(CO)30]2a-n d its decarbonylation at 120 'C under vacuum were characterized infrared and X-ray absorption spectroscopies. The decarbonylated cluster had an average Pt-Pt bond distance of 2.76 and an average Pt-Pt first-shell coordination number of 3.7, indicating that the trigonal prismatic framework structure the Longoni-Chini cluster was retained after decarbonylation; thus the decarbonylated cluster is represented as PtIS with trigonal prismatic structure. When this sample was recarbonylated, the Longoni-Chini cluster was not re-formed. The Pt-Pt bond distance increased to 2.78 A and the Pt-Pt first-shell coordination number increased to 6.0, indicating a CO-induced morphology change gave approximately hemispherical Pt clusters with adsorbed CO.
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Chang et al. (1992) studied this question.